scholarly journals Crack Detection through the Change in the Normalized Frequency Shape

Vibration ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 56-68
Author(s):  
Mustapha Dahak ◽  
Noureddine Touat ◽  
Tarak Benkedjouh
Keyword(s):  
Stiffness Matrix ◽  
Electrical Discharge ◽  
Inverse Method ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Electrical Discharge Machining ◽  
Element Model ◽  
Experimental Application ◽  
Flexibility Matrix ◽  
Crack Position

The objective of this work is to use natural frequencies for the localization and quantification of cracks in beams. First, to study the effect of the crack on natural frequencies, a finite element model of Euler–Bernoulli is presented. Concerning the damaged element, the stiffness matrix is calculated by the theory of fracture mechanics, by inverting the flexibility matrix. Then, in order to detect damage, we are going to show that the shape given by the change in the natural frequencies is as function of the damage position only. Thus, the crack is located by the correlation between the shape of the measured frequencies and those obtained by the finite elements, where the position that gives the calculated shape which is the most similar to the measured one, indicates the crack position. After the localization, an inverse method will be applied to quantify the damage. Finally, an experimental application is presented to show the real applicability of the method, in which the crack is introduced by using an Electrical Discharge Machining. The results confirm the applicability of the method for the localization and the quantification of cracks.

Natural Vibrations of a Clamped-Clamped Arch With an Open Transverse Crack

1997 ◽  
Vol 119 (2) ◽  
pp. 145-151 ◽  
Author(s):  
M. Krawczuk ◽  
W. Ostachowicz
Keyword(s):  
Finite Element ◽  
Stiffness Matrix ◽  
Edge Crack ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Curved Beam ◽  
Natural Vibrations ◽  
Crack Location ◽  
Cracked Arch

The paper presents a finite element model of the arch with a transverse, one-edge crack. A part of the cracked arch is modelled by a curved beam finite element with the crack. Parts of the arch without the crack are modelled by noncracked curved beam finite elements. The crack occurring in the arch is nonpropagating and open. It is assumed that the crack changes only the stiffness of the arch, whereas the mass is unchanged. The method of the formation of the stiffness matrix of a curved beam finite element with the crack is presented. The effects of the crack location and its length on the changes of the in-plane natural frequencies and mode shapes of the clamped-clamped arch are studied.

scholarly journals RESONANT AND ANTIRESONANT FREQUENCIES OF MULTIPLE CRACKED BAR

2019 ◽  
Author(s):  
Nguyen Tien Khiem ◽  
Ba Lien Thi Pham
Keyword(s):  
Frequency Response ◽  
Arbitrary Number ◽  
Frequency Response Function ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Resonant Frequencies ◽  
New Form ◽  
Analysis Of Variation ◽  
Crack Position ◽  
Resonant And Antiresonant Frequencies

The natural frequencies or related resonant frequencies have been widely used for crack detection in structures by the vibration-based technique. However, antiresonant frequencies, the zeros of frequency response function, are less involved to use for the problem because they have not been thoroughly studied. The present paper addresses analysis of antiresonant frequencies of multiple cracked bar in comparison with the resonant ones. First, exact characteristic equations for the resonant and antiresonant frequencies of bar with arbitrary number of cracks are conducted in a new form that is explicitly expressed in term of crack severities. Then, the conducted equations are employed for analysis of variation of resonant and antiresonant frequencies versus crack position and depth. Numerical results show that antiresonant frequencies are indeed useful indicators for crack detection in bar mutually with the resonant one

Influence of Interfacial Bond Strength on the Mechanical Properties of Resin Mineral Composite Reinforced by Molybdenum Fibers

2012 ◽  
Vol 602-604 ◽  
pp. 41-44
Author(s):  
Ze Ning Wang ◽  
Jian Hua Zhang ◽  
Xiu Hua Ren ◽  
Tao Wang ◽  
Xiao Quan Tian
Keyword(s):  
Mechanical Properties ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Simulation Analysis ◽  
Element Model ◽  
Resin Matrix ◽  
Wire Electrical Discharge Machining ◽  
Strengthening Effect ◽  
Interfacial Bond Strength ◽  
Bond Slip

To improve the poor mechanical properties of resin mineral composite, molybdenum fibers reinforced technology and mechanism are researched. The micro-surface morphology of new and wire electrical discharge machining used molybdenum fibers are analyzed, and the cohesive reinforce mechanism is deduced respectively. Two-dimensional simplified finite element model of resin mineral composite reinforced by molybdenum fibers is established for the simulation analysis of bond-slip of interface between fiber and resin matrix. Tests on the internal stress distribution of resin mineral composite without fibers and resin mineral composite reinforced by molybdenum fibers are carried out. Research results show that the addition of molybdenum fibers can effectively restrict the deformation of composite, and the randomly distributed pits on the surface of wire electrical discharge machining used molybdenum fibers can enhance the strengthening effect and reduce the cost of composite.

Vibration Analysis of Rotor With Transverse Surface Cracks

2003 ◽  
Author(s):  
Dan Guo ◽  
Fu-Lei Chu ◽  
Yong-Yong He
Keyword(s):  
Stiffness Matrix ◽  
Vibration Analysis ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Surface Cracks ◽  
Breathing Crack ◽  
Cracked Rotor ◽  
Six Degrees Of Freedom ◽  
Flexibility Matrix ◽  
Vibration Responses

The vibration of cracked rotor is investigated by numerical method. The FEM is used to model the rotor with cracks. Six degrees of freedom are considered in each elemental node. Full 6×6 flexibility matrix is deduced by Papadopoulos and Dimarogonas’ method, and 12×12 stiffness matrix of cracked element is derived. The influence of one or more cracks on the natural frequencies and different modals (including bending modal, torsion modal and longitudinal modal) of cracked rotor is explored. Vibration responses of rotor with open cracks or breathing crack loading by eccentric force and rotor gravity force are obtained and analyzed by numerical integer method and spectral technology. The coupling of lateral, longitudinal and torsion vibrations due to transverse surface crack is studied. It is concluded that the above research is useful in detecting crack in rotor.

Spatial combined cable element for cable-supported bridges

2018 ◽  
Vol 36 (1) ◽  
pp. 204-225 ◽  
Author(s):  
Jiandong Wei ◽  
Manyu Guan ◽  
Qi Cao ◽  
Ruibin Wang
Keyword(s):  
Stiffness Matrix ◽  
Design Methodology ◽  
Element Model ◽  
Suspension Bridges ◽  
Force Vector ◽  
Content Type ◽  
Flexibility Matrix ◽  
Arch Bridges ◽  
The Finite Element Model ◽  
Cable Stayed Bridges

Purpose The purpose of this paper is to analyze the cable-supported bridges more efficiently by building the finite element model with the spatial combined cable element. Design/methodology/approach The spatial combined cable element with rigid arms and elastic segments was derived. By using the analytical solution of the elastic catenary to establish the flexibility matrix at the end of the cable segment and adding it to the flexibility matrix at the ends of the two elastic segments, the flexibility matrix at the end of the cable body is obtained. Then the stiffness matrix of the cable body is established and the end force vector of cable body is given. Using the displacement transformation relationship between the two ends of the rigid arm, the stiffness matrix of the combined cable element is derived. By assigning zero to the length of the elastic segment(s) or/and the rigid arm(s), many subdivisions of the combined cable element can be obtained, even the elastic catenary element. Findings The examples in this field and specially designed examples proved the correctness of the proposed spatial combined cable element. Originality/value The combined cable element proposed in this study can be used for the design and analysis of cable-stayed bridges. Case studies show that it is able to simulate cable accurately and could also be used to simulate the suspenders in arch bridges as well in suspension bridges.

Lowest Natural Frequencies of Structures With Rigid-Body Degrees of Freedom

1968 ◽  
Vol 12 (02) ◽  
pp. 131-136
Author(s):  
S. Hylarides
Keyword(s):  
Rigid Body ◽  
Stiffness Matrix ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Power Method ◽  
Flexibility Matrix ◽  
Numerical Operations

To calculate the lowest natural frequencies, use can be made of the power method, for which the flexibility matrix or the inverted stiffness matrix has to be available. Structures with rigid-body degrees of freedom, however, have a stiffness matrix which is not invertible. In this paper three methods are described to derive from the singular stiffness matrix a regular one. These methods are based on the same principles, but differ in particulars. One method is recommended, since it involves less numerical operations, while its accuracy is the same.

Tribocorrosion Properties of Titanium Alloy Modified By Electrical Discharge Machining

2017 ◽  
Author(s):  
Bruna Michelle de Freitas ◽  
Carlos augusto Henning Laurindo ◽  
Paulo Soares ◽  
Leticia Bemben
Keyword(s):  
Titanium Alloy ◽  
Electrical Discharge ◽  
Electrical Discharge Machining

Optimization of the Electrical Discharge Machining of Complex Components

2020 ◽  
Vol 40 (10) ◽  
pp. 870-872
Author(s):  
T. R. Ablyaz ◽  
E. S. Shlykov ◽  
K. R. Muratov
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Complex Components
Sign in / Sign up

Export Citation Format

Share Document